Why In2O3 Can Make 0.7 nm Atomic Layer Thin Transistors

Mengwei Si; Yaoqiao Hu; Zehao Lin; Xing Sun; Adam Charnas; Dongqi Zheng; Xiao Lyu; Haiyan Wang; Kyeongjae Cho; Peide D Ye

doi:10.1021/acs.nanolett.0c03967

Why In₂O₃ Can Make 0.7 nm Atomic Layer Thin Transistors

Nano Lett. 2021 Jan 13;21(1):500-506. doi: 10.1021/acs.nanolett.0c03967. Epub 2020 Dec 29.

Authors

Affiliations

¹ School of Electrical and Computer Engineering and Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907, United States.
² Department of Materials Science and Engineering, The University of Texas at Dallas, Richardson, Texas 75080, United States.
³ School of Materials Engineering, Purdue University, West Lafayette, Indiana 47907, United States.

PMID: 33372788
DOI: 10.1021/acs.nanolett.0c03967

Abstract

In this work, we demonstrate enhancement-mode field-effect transistors by an atomic-layer-deposited (ALD) amorphous In₂O₃ channel with thickness down to 0.7 nm. Thickness is found to be critical on the materials and electron transport of In₂O₃. Controllable thickness of In₂O₃ at atomic scale enables the design of sufficient 2D carrier density in the In₂O₃ channel integrated with the conventional dielectric. The threshold voltage and channel carrier density are found to be considerably tuned by channel thickness. Such a phenomenon is understood by the trap neutral level (TNL) model, where the Fermi-level tends to align deeply inside the conduction band of In₂O₃ and can be modulated to the bandgap in atomic layer thin In₂O₃ due to the quantum confinement effect, which is confirmed by density function theory (DFT) calculation. The demonstration of enhancement-mode amorphous In₂O₃ transistors suggests In₂O₃ is a competitive channel material for back-end-of-line (BEOL) compatible transistors and monolithic 3D integration applications.

Keywords: charge neutrality level; enhancement-mode; indium oxide; oxide semiconductor; thin-film transistor; ultrathin body.